Home > Cognitive Bias, Decision Making, Education > Handwashing, Heliocentrism, and Global Warming: To Reject or Accept?

Handwashing, Heliocentrism, and Global Warming: To Reject or Accept?

How often do you wash your hands? The Center for Disease Control recommends hand washing in numerous scenarios, such as before, during, and after preparing food, before and after tending to someone who is sick, before and after treating a wound, after going to the bathroom, after touching animals, and the list goes on. Now I know it might seem a little ridiculous to wash your hands as often as it is recommended, but I am crossing my fingers that you at least understand why it is necessary. One of the first things we teach our children is to always wash their hands, and how to do so effectively (such as washing for the duration of “Row, Row, Row Your Boat”… twice). If you don’t believe me when I say hand washing is deep-seated in our modern society, just look at the 3.1 billion dollar market for hand soaps (Nielsen 2016). I, for one, certainly get overwhelmed when I walk down the aisle at my local Target and have to choose between the exhaustive collection of soaps with which I can lather up. And if I don’t find any soap I like then I can make my way over to the various types of hand sanitizers nearby. We can credit Ignaz Semmelweis and his microbial discoveries for the normalization of hand washing in our culture, but can you imagine a world where we didn’t wash our hands? And even stranger – can you imagine rejecting the science behind it? 

Semmelweis was one of the most influential doctors in the creation of modern germ theory. His interest in the topic was spiked when he started to theorize why the mortality rate was three times higher when obstetricians preformed child deliveries compared to midwives (Walker and Wilson 2014). His reasoning was that the doctors were contaminated by working with cadavers, and would spread the germs during the delivery process because they did not wash their hands. When he introduced a chlorinated solution for doctors to wash their hands before treating a patient, the mortality rates significantly dropped (Wyklicky and Skopec 1983). Even though there was clear evidence supporting the benefits of hand washing, majority rejected his idea because they firmly believed a man’s hand could do no harm. However, germ theory was not the only scientific result of Semmelweis’ research. Psychologists noticed a cognitive bias, or an error in thinking, in the public’s reaction to his work and aptly named it the Semmelweis Reflex. This reflex is to reject new and sound evidence and research because it conflicts with strongly held beliefs (Fedoroff, Curry, Ranger, et al. 2016). 

This is almost interchangeable with the theory of belief perseverance in psychology. This concept argues that a person is more likely to reject information if it doesn’t align with their own views, and accept information if it does align. While there are three types of belief perseverance, the third type, which focuses on theories and hypotheses most closely, is most similar to the Semmelweis Reflex because it more specifically relates to scientific studies. The other two types of perseverance bias focus on social experiences and personal identity. This belief, while limiting universal process, can also have profound individual effects such as eating disorders and misconstrued ideas of selfhood (Anderson and Lindsay 1998).

Cognitive psychology studies how information gets processed from the environment and used. It looks at processes such as attention, memory, pattern recognition, categorization and language. Of all the cognitive biases, the Semmelweis reflex occurs most often when presented with too much information. The brain uses this reflex to filter out “useless” information, and filter in information that pertains to our preconceived ideas and knowledge. We are naturally attracted to the information that confirms these beliefs, and, as per the Semmelweis reflex, tend to ignore the information that contradicts these beliefs. This effect relies on automatic processing, which quickly and effortlessly accepts or rejects the ideas.

Now, you may be wondering why this is important, asides from the introduction of compulsive hand washing in our society of course. In fact, this effect can be seen all throughout history – both before and after it was first noted in Semmelweis’ process. One of the major examples of this reflex should sound quite familiar – the argument that Earth rotates around the sun, and that it is not the center of the universe. Heliocentric ideas were not fully accepted until after Copernicus popularized the idea, but it had been theorized many years prior by the ancient Greek writer Aristarchus in 270 B.C. Aristarchus had introduced the idea, but it was rejected by many, due in part to the unnoticed Semmelweis reflex.

This is even more relevant in today’s society where we now have advanced enough technology to make important scientific discoveries. If you go onto NASA’s website, you will see in bold letters atop of a long list of facts, “Scientific consensus: Earth’s climate is warming.” Trust me – its there. Why is it then, that a couple clicks away on another government website you find Senator James Inhofe, climate change denier, saying, “It is mystifying that some people blithely assert that the science of global warming is settled.” Without getting into the political reasoning behind the denial of climate change, which there are arguably many, this separation of views can scientifically be explained by the effect the Semmelweis Reflex. People are rejecting scientific proof because it does not align with their own beliefs, and applied top-down mental processing.

The Semmelweis reflex can often be confused with stubbornness and close-mindedness, but should simply be seen as one of the mind’s first defenses against the overwhelming amount of information in this world. The key to progress and pushing society forward is to control this reflex and be able to look past cognitive biases at large in order to accept what we might not first instinctively believe. So next time, after washing your hands and arguing about climate change, think about what else you might be ignoring and rejecting simply because it doesn’t fit your world views.


Anderson, C. A., & Lindsay, J. J. (1998). The development, perseverance, and change of naive theories. Social Cognition, 16, 8-30.

Experimentation Platform. (n.d.). Retrieved April 17, 2017, from http://www.exp-platform.com/Pages/SemmelweisReflex.aspx
Fedoroff, J.P., Curry, S., Ranger, R. et al. Arch Sex Behav (2016) 45: 1869. doi:10.1007/s10508-016- 0786-3
Inhofe, J. M. (n.d.). The Facts and Science of Climate Change (United States., Congress., Senate.).
International Space Hall of Fame :: New Mexico Museum of Space History :: Inductee Profile. (n.d.). Retrieved April 17, 2017, from http://www.nmspacemuseum.org/halloffame/detail.php?id=123
Shaftel, H., & Tenenbaum, L. (Eds.). (2017, April 10). Global Climate Change; Vital Signs of the Planet. Retrieved April 17, 2017, from https://climate.nasa.gov/scientific-consensus/
Statistic Brain Research Institute. (2016, February 02). Soap Industry Statistics. Retrieved April 17, 2017, from http://www.statisticbrain.com/soap-industry-statistics/
Understanding the Semmelweis Reflex. (n.d.). Retrieved April 17, 2017, from http://iqsresearch.com/understanding-the-semmelweis-reflex/
Walker, D. A. and Wilson, P. (2014), Learning from Semmelweis: engaging in sensible infection control. Anaesthesia, 69: 807–810. doi:10.1111/anae.12771
Wash Your Hands. (2017, April 10). Retrieved April 17, 2017, from https://www.cdc.gov/features/handwashing/
Wyklicky, H., & Skopec, M. (1983). Ignaz Philipp Semmelweis, the Prophet of Bacteriology. Infection Control, 4(5), 367-370. Retrieved from http://www.jstor.org.colby.idm.oclc.org/stable/30142576

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  1. smcramer
    May 12th, 2017 at 19:16 | #1

    To answer your question about whether or not the Semmelweis effect could explain why someone ignores evidence after repeated exposure, I think it still would. While it is an automatic process, I think there are also more controlled aspects to it. These controlled processes could account for the active rejecting of present material if it doesn’t match your views. Also, while I do believe some exposure to germs is necessary for the development of a healthy and strong immune system, I think in certain cases (particularly those pertaining to the medical field) you should definitely wash your hands.

  2. seseid20
    April 29th, 2017 at 21:31 | #2

    Last line a little louder for the people in the back! This post is so relevant today because I really do think many people struggle to understand how others can fail to see facts right in front of their faces. You talk about this bias being attributed to automatic processing. This makes sense because I think often people do tend to make these judgments against new information very quickly, however, I am wondering how this translates to more long-term exposure to ideas. For example, you mentioned the sites talking about climate change, and I think often times people just click away from the information that does not fit their beliefs. But what about when someone is constantly exposed to an alternative view and they continue to reject it. Is this till the Semmelweis Reflex or is it a different bias because it is no longer just an automatic, time-saving process? Also, hand-washing is for the weak. The way I was brought up was to be always eating/touching germy things and if I get sick or die from something, I should appreciate that germ’s strength.

  3. abgrossm
    April 29th, 2017 at 18:02 | #3

    I thought your blog post was very interesting, because I have often wondered if there are things that are agreed upon by a majority of people in 2017 that 50 or 100 years from now people will find hard to believe that anyone ever thought that. Your post also reminded of some older people I know who have a very hard time believing in climate change.
    Reading your post I was reminded about what I read about in Andrew’s post (Why Students of Politics Should Leave the Colby Hill: The Confirmation Bias), where he discussed how confirmation bias may have been a reason that Hilary Clinton supporters were so shocked by Donald Trump’s win. Just like people who supported Hilary may have chosen to focus on aspects of the campaign and polls that would suggests that Hilary was going to win, if you believe that climate change is not real you will probably selectively focus your attention on any evidence that you can find in favor of your position. It seems as if the confirmation bias could be a way to help you reinforce the Semmelweis Reflex. If you focus your attention on any evidence that exists against climate change, you will probably feel even more confident rejecting climate change if it is against your beliefs.
    You mentioned how a possible reason for the bias could be that when we have too much information to possibly all be processed, we selectively filter for the information that matches our current beliefs. This reminded me of the Treisman’s filter attenuation model of attention that we discussed in class. In those models, information that is very relevant to you or the context you are in will be closer to a threshold, and it will have a higher likelihood of crossing the threshold and becoming the focus of your attention (Treisman, 1960). In this case the information that is close to the threshold would be information that is consistent with your beliefs, and you would push the information that is inconsistent with your beliefs farther away from the threshold. This would allow you to focus your attention mostly on information that is consistent with your current beliefs and expectations. Although it is not exactly the same, based on what you wrote about it seems like a model similar to the early attention filter models could possibly explain the Semmelweis Reflex.

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